1. Field of the Invention
The present invention relates to a valve timing control device to be used for controlling the opening/closing timing of an intake valve or an exhaust valve in a valve actuating mechanism of an internal combustion engine.
2. Description of the Related Art
In Unexamined Published Japanese Patent Application No. Hei 1-92504 or Unexamined Published Japanese Utility Model Application No. Hei 2-50105, for example, there is disclosed a valve timing control device of that kind comprising: a valve opening/closing rotary shaft rotatably assembled with the cylinder head of the internal combustion engine; a rotor integrally provided on the rotary shaft; a timing pulley for transmitting rotational power from a crank pulley through a timing belt; a rotational transmitting member integrally provided within the timing pulley, which is mounted around the peripheral surface of the rotary shaft, so as to rotate within a predetermined range for transmitting the rotational power from the crank pulley; a plurality of vanes provided on the rotor or the rotational transmitting member; a fluid chamber formed between the rotor and the rotational transmitting member and separated into advancing chambers and delaying chambers by the vanes; first fluid passages for feeding and discharging a fluid to and from the advancing chambers; and second fluid passages for feeding and discharging the fluid to and from the delaying chambers.
In the valve timing control device, as described in each of the above-cited patent applications, the rotational transmitting member includes an external rotor, a front plate and a rear plate. The fluid chamber is formed between the rotor and the external rotor and separated into advancing chambers and delaying chambers by the vanes. Working fluid is fed to or discharged from the advancing chambers and delaying chambers. The timing pulley is disposed outside of the external rotor.
The timing belt is located between the crank pulley and the timing pulley. The timing belt, the crank pulley and the timing pulley are all disposed in a timing belt case. The timing belt case is attached on the side of the cylinder block and on the front side of the cylinder head. When the internal combustion engine is driven, the temperature of the atmosphere inside the timing belt case reaches about 80 degrees centigrade. On the other hand, the working fluid, which is used as lubricating oil, reaches from about 120 degrees centigrade to 130 degrees centigrade, when the internal combustion engine is driven. In the valve timing control device, as described in each of the above-cited patent applications, the working fluid heats the rotational transmitting member and the timing pulley. This heat might damage the timing belt made of a resin or a rubber and shorten the lifespan of the timing belt.